It is known to convert cyanuric chloride in vapor form and obtained by trimerization of cyanogen chloride into solid fine-particle cyanuric chloride directly or via liquid cyanuric chloride:
The precipitation of pulverulent cyanuric chloride by desublimation of cyanuric chloride in vapor form may take place in externally cooled chambers or by introducing the cyanuric chloride vapor into a precipitation chamber with an inert gas and/or an inert coolant which evaporates in the precipitation process--see for example DE-PS 12 66 308 and U.S. Pat. No. 4,591,493. To obtain fine-particle cyanuric chloride from liquid cyanuric chloride the latter is sprayed into a precipitation chamber and cooled in the precipitation chamber with circulated inert cooling gases or by indirect cooling until the spray droplets precipitate in crystalline form--see for example DE 28 43 379. Considerable technical outlay for precipitation chambers and devices for recycling and cleaning process and waste gases is common to the processes.
In the processes which have been appreciated in the past and are based on the same principles, cyanuric chloride is always obtained in fine-particle form, generally with a maximum particle diameter substantially below 250 .mu.m. Although such fine-particle products are advantageous as regards their high reactivity they have a number of drawbacks which make another product form desirable for many purposes.
The handling, such as feeding, storing and metering, of fine-particle cyanuric chloride poses particular problems because the corrosive and irritant properties accompany the conventional dust formation of fine-particle substances which requires extraction devices. Furthermore, cyanuric chloride is sensitive to hydrolysis, wherein hydrolysis products formed thereby can contaminate not only cyanuric chloride itself, but also subsequent products produced therefrom. Because of its high surface, cyanuric chloride is particularly accessible to hydrolysis. This also means that solid deposits in the dust removal devices and dust-carrying pipes can easily occur. Technically complex measures and/or fittings are required in order to prevent faults and eliminate those which have occurred.
A further drawback of fine-particle cyanuric chloride is the unsatisfactory flowability. Although this can be improved by the addition of free-flow auxiliary substances, such as silicas, the free-flow auxiliary substance reduces the product purity of the cyanuric chloride and optionally also that of the products produced from it. According to EP-A 0 416 584 the flowability of solid cyanuric chloride produced by desublimation or spray crystallization may also be improved without the addition of a free-flow auxiliary substance, by a shear treatment thereof in a kneader or mixer, particularly at 60 to 120.degree. C.; the finely powdered nature of the cyanuric chloride is not, however, eliminated by this process as the average particle size of exemplary embodiments is in the range from approximately 10 .mu.m to 40 .mu.m.
The as yet unpublished German patent application 196 42 449.6 discloses flake and pellet-shaped cyanuric chloride moldings. These moldings may be produced by applying molten cyanuric chloride in drop or strip form to a surface and removing the heat of fusion by cooling the surface or contacting the melt applied to the surface with a coolant gas. A drawback of this process is that the device with the cooling belt must be designed in enclosed form. Furthermore, because of the high sublimation vapor pressure of cyanuric chloride in the vicinity of the solidification point and also above 100.degree. C. considerable sublimation takes place and hence formation of fine-particle material.